Variable-load brake



Patented Feb. 9, 1926.

UNITED STATES PATENT OFFICE.

CLYDE C. FARMER, OF PITTSBURGH, PENNSYLVANIA. ASSIGNOR TO THE WESTING-HOUSE AIR BRAKE COMPANY, OF WILMEBDING, PENNSYLVANIA,- A CORPORA- TIONOF PENNfiYLVANIA.

VARIABLE-LOAD BRAKE. i

Application filed April 10, 1925. Serial No. 22,074.

To aZZ 107mm it vim-y 0012mm:

Be it known that I, CLYDE C. Fanrnnua citizen of the United States,residing at Pittsburgh, in the county of Allegheny and State ofPennsylvania, have invented new and useful Improvements in Variable-LoadBrakes, of which the following is a specification. y

This invention relates to fluid pressure brakes and has particularreference to load regulated brakes. I

It has heretofore been proposed to provide a load regulated brakeequipment having means adapted to be adjusted so as to regulate thebraking power according to the load on the car and including a springadapted to be compressed in proportion as the load is increased.

The compression of the spring by the load on the car is effected througha system of levers, which may be thrown into and out of operativerelation by the operation of a fluid pressure piston, so that the leversystem may be maintained in its inactive position while the car isrunning and thus prevent the spring from being acted upon by the load011 the car except when the car is stopped. In order to lock the springso that it will remain in its adjusted position while the car isrunning, a locking device is provided.

In previousequipments of this type, the locking means is released at thesame time that the system of levers is thrown into po sition to permitthe load on the car to act on the regulating spring. Accordingly, whenthere is a load on the car and the regulating spring is correspondinglycompressed, as soon as the locking means is released, the pressure ofsaid compressed spring will suddenly react through the system of leversso as to bring the cam member into engage ment with the member carriedby the car truck, with an undesirable hammer bloW.

The principal object of my invention is to provide means for obviatingthe above diiiiculty.

Other objects and advantages will appear from the following moredetailed descrip tion of the invention.

In the accompanying drawing; Fig. 1 is a diagrammatic sectional view ofa load brake apparatus embodying my invention;

service and Fig. 2 a detail view of the adjusting means carried by thecar body and the car truck.

I According to my invention I provide means for maii'itaining the systemof levers in locked position until after the cam member, which iscarried by the car body, has been brought into engagement With themember carried by the cartruck.

As shown in the drawing, the equipment may comprise a brake cylinderpressure limiting valve device 1, a brake cylinder supply valve device2, a locking mechanism 3, a strut cylinder 1, and a brake cylinder 5.

The brake cylinder pressure limiting valve device 1 may comprise aflexible diaphragm 6, which is subject on one side to the pressure offluid in the brake cylinder 5, as supplied through passage 7 fromchamber 8, and on the opposite side to the pressure of a coil spring 9.A plunger 19 engaging the free end of the spring 9 is provided 111 orderto vary the pressure exerted by said spring; The flexible diaphragm (Sisadapted to op-- erate a valve 10, which controls the operation of thebrake cylinder supply valve 2.

The brake cylinder supply valve 2 may comprise a valve piston 11 subject011 one side to the pressure or a spring 12 and on the inner seated areaof the opposite side to the pressure of fluidlin a chamber 13, which isconnected by passage and pipe 14 to the porto't the brake applicationvalve, (not shown). 7

Pivotally mounted on the cap of the strut cylinder 4 is a crank armmember having crank arms 15, 16, and 17. A roller 18 pivotally mountedon the crank arm 15 is adapted to engage one end of the plunger 19 foreffecting an adjustment of the spring 9, according to the load on thecar.

The crank arm 16 is connected by link 20 to a ratchet bar 21,'whi.ch is'slidably mounted in the locking mechanism casting. The teeth 22 of theratchet bar 21 are engageable by a pawl 23, which is operativelyconnected to a piston 24. The piston 24 is subject on one side to thepressure of a spring 25 and on the opposite side to the pressure offluid as supplied through passage 26 from a valve device 27.

The valve device 27 may comprise a valve piston 28 subject on one sideto. the pressure of a spring 29 and on the inner seated area :ot' theopposite side to the rpressu-re ot' fluid in passage and pipe 30,=Wl11'Cl1 1s connected to the usual door opening "pipe, Secured to theseating face of the valve piston-28is a stem member 81, Which engagesa-ball check valve 32and'is adapted "when said valve piston is heldseated by the spring 29 to hold the ball check 32 from itsseat.

The strut cylinder 4; is carried by the looking mechanism casting andcontains a ;piston 34, the stem of which is pivotally connectedtea-lever The lever 35 ispivotally connected; at: one end :t-o'aarod 36,and 15 at the other end to a rod 37, which inturn ispi-votallyconnectedito the crank arm 17. The outer end of the rod 36 -is pivotallyconnected to oneearm 38 Offid bell crank, which is -mounted on the carbody. The vother :arm 39'of the bell crank is adapted uponoutward:movement o'tithe rodf36 to engage-=21- member 40 -.mounted onthe car truck. 1

.In operation, when the -car doors are 25 opene'chfiuid under pressureis supplied in .theiusual Way to thedoor opening ,pipe and --eonsequently to pipe and passage 30. The -val-ve piston .28 being held seated bythe pring 29, fluid from passage flows-past 30 .ballvcheck32 to' passage.41 and thence to the strut cylinder 33. i f

The fluid nnderpressure buildingiup in cylinder-33 forces the piston 34outwardly against the pressure exerted by spring 42. 35 Theipavvl23being held-in-engagementavith teeth 22 of'l-atch bar 21,.by'the spring25, the crank arms 15, 16, and 17 are held against movement,so that thepivot pin 43 \.'-ill act.as a fulcrum foritheilever 35, and the outwardmovement of piston 34 will push therod' EEG-soas to bring crank arm 39into engagement with the member 40.

The-spring .29 is of such resistance was to hold the valve piston-2-8-seated, against the vpressure ot fluid acting on the inner-seatedarea of the opposite side. nntilthepresshre =of fluid "in thestrutieylinder 4 and consequently on'the inner seated area of said-valvepiston has built up suflicientl y tomove the piston 34. outwardly, at.which time said valve piston will be unseated against the pressureexerted by thespring 29. V

The unseatingeofvalve piston 28 permits the ballchesk 3-2 to seat,thereby-preventing back tlovvot fluid from cylinder 4 and-:at the sametime opens communication from passage 30 and the door opening pipe,through passage 26., to oneside of piston v2st. The fluid under pressuresuppliedfrom passage 30 acting on piston 24 moves said piston to theright against the pressure ex;-

erted by the spring 25 so asto: disengage the pawl 23 from the teeth 22of ,r-atchet-bar-21. It the load on the car is now increased, the carsprings will becompressed, so :that

the member 40 acting on the arm 39 will cause acounterclockwisemovement'of the bell crank, which exerts a force throughtherod 36 to cause a clockwise rotation of the lever 35, with the pivotpin 45 acting as a fulcrum. "The ro'd'37then acts torotate crankarm'lTso as to rock'the cranka'rm 15 in a clockwisedi-rection,"forcing'the plunger 19 -upwardly to compress the spring 9 correspondingly withthe increase in load.

\Vhenthetcar.has been loaded and the car doors are closed, the dooropening pipe is connected to atmosphere in theusual opcrationof the doorcontrola pparatus,:so that :fluid actinp on: the latch piston 2t mayflow through passage 26 past unseated-valve pis- 1 ton 28,thence-through passage and pipe 30 andt-he door opening pipe toatmosphere, thereby -.permitting-thespring 25 to Fiorce the piston '24to the left and causepaivl 23 to-en-ga ge the teeth-0t rack bar 21.

Thexball check 32 preventsthe escape of fluid from the strut cylinder'3'3'until :after the pressure in thedooropeningpipe and consequently inpassages "26 :and 30 has been reduced to a degree slightly less than the,pre sure exerted by sprin-g29, at Whiehitime said spring avill-seat thevalve piston 28, .thereby unseatingr ballcheck 32 and'permitting fluidfrom cylinder 33-to-floiv to atmosphere by ava-yof passages '41 and :30and the door openingpipe. r

, It willanoivbeseenthat thepiston 34;is .n'mintained in its outermostposition until after the ,piston 24:has movedto the left, gcau-singz'pawl 23-to-en qage the teeth22 of the ratchet bar21, therebylockingthemec'hanism i n: adj ustechposition. 1t aservice brakeapplication is efi'eeted in order :to bring the car itoia stop at thenext loading place, fluid under pressure from the brake applicationvalve '(notshoivn) will be supplied through pipe 14 to chamber 1 3-.where it acts on the exposed :area of valve piston -11. rSaid *-alvepiston istheu unseated,permittingfiuidito flow to chamber 8, thence-:throug5h gpassage .46 and pipe .4? to the brake cylinder Fluid ifi-omchamber 13 also equalizes through choked port-48 to the spring side ofvvalve ,piston 28 and escapes therefrom through v 'iassa-ge 49, pastunseated valve 10, through passage 7 to chamber 8, and thence through,passageand pipe 47 to the bra-kc cylinder 5.

The pressure of fluids-applied to thebrakc cylinder is also suppliedthrough passage ,7 todiaphragm 6 and when the-pressure in the brakecylinder has been increased'to a predetermined degree, correspondingWith the -,previous adjustment of spring '9 in .accordance with theloadion thecar, saiddiaphragm will be moved downwardly, gpermib ting thevalve lO'toi-he-seated by itsspring. Sincethesea-ting of'the valve 10prevents further escape of fluid under pressure from the spring side ofthe valve piston 28, fluid quickly equalizes on opposite sides thereof,so that the spring 12- will seat said valve piston and prevent furtherflow of fluid under pressure to the brake cylinder.

It will be evident that the apparatus will operate in a similar mannerto reduce the pressure of spring 9 when the load on the C21 isdecreased, since under such a condition the crank arm 15 would be rockedin a counter-clockwise direction corresponding to the relative positionsof the arms 39 and member 40.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent, is

1. In a load brake, the combination with means adjustable according tothe load on the car for regulating the braking power, of fluid pressureoperated means for locking said adjustable means in an adjustedposition, means operated by fluid under pressure for operativelyconnecting up said adjustable means so as to be adjusted according tothe load on the car, and means for supplying fluid under pressure tosaid locking means upon a predetern'iined increase in pressure of fluidsupplied to said operatively connecting means. 7

2. In a load brake, the combination with means adjustable according tothe load on the -car for regulating the braking power, of a lockingdevice for locking said means in an adjusted position, and operated byfluid under pressure to release said locking device, a piston operatedby fluid under pressure for operatively connecting said means so as tobe controlled according to the loadon the car, and means operated byfluid supplied to said piston for controlling the supply 0t fluid tosaid locking device.

3. In a load brake, the combination with means adjustable according tothe load on the car for regulating the braking power, of a lockingdevice for locking saidmeans in an adjusted position and movable to arelease position, mechanism movable to a position for operativelyconnecting said means so as to be adjusted according to the load on thecar. and means for effecting the movement of said mechanism to saidposition in advance of the HIOVBHIEHtof said locking device to releaseposition. i

4. In a load brake, the combination with means adjustable according tothe load on the car for regulating the braking power, of a lockingdevice for locking said means in an adjusted position, and operated byfluid under pressure to release said locking device, a piston operatedby fluid under pressure for operatively connecting said means so as tobe controlled according to the car for regulating the braking power,

of a locking device for locking said means in an adjusted position andreleased by fluid under pressure, and means operated upon apredetermined increase in fluid under pressure for supplying fluid tosaid locking de vice;

6. In a load brake, the combination with means ad ustable according tothe load on the car for regulating the braking power,

of a locking device for locking said means in an adjusted position andreleasable by fluid under pressure, and a Valve piston subject on oneside to the pressure. of a spring and operated by fluid under pressuresupplied to the opposite side for supplying fluid under-pressure to saidlocking device.

7. In a load brake, the combmation with means adjustable according totheload on the car for regulating the braking power, of a locking devicefor locking said means in an adjusted position and releasable by fluidunder pressure, valve means operated by fluid under pressure forsupplying fluid to said locking device and means controlled by saidvalve means for controlling the re lease of fluid from said piston.

8. In a load brake, the combination with means adjustable according tothe load on the ear for regulating the braking power, of a lockingdevice for locking said means in an adjusted position and releasable byfluidunder pressure, valve means operated by fluid under pressure forsupplying fluid to said locking device, and a check valve controlled bysaid valve means for controlling the release of fluid frolnsaid piston.

9. In a load brake, the combination with means adjustable according tothe load on the car for regulating the braking power, of a lockingdevice for locking said means in an adjusted position and movable to arelease position, mechanism movable to a position for operativelyconnecting said means so as to be adjusted according to the load on thecar, and means for effecting the movement of said mechanism to saidposition in advance of the movement of said locking device to releaseposition and for effecting the movement of said locking device to itslocking position in advance of the movement of said mechanism from itsoperatively connecting position.

In testimony whereof I have hereunto set my hand.

CLYDE G. FARMER.

